We are a group of investigators with long-term collaborations centering on our common interest in metabolic disease and atherosclerosis. The Davis lab's contribution to the technical expertise of the group has been to provide lipid quantitation and oxysterol analysis using gas/liquid chromatography and GC/mass spectroscopy. The purpose of this application is to seek funds to procure a GC/mass spectrometer allowing us to analyze cells, tissues and isolates for lipids, sterols and metabolites. In addition, this machine will enable us to perform stable isotope dilution analysis in order to assess how phenotype (i.e. the in vivo metabolism of lipids, sterols and metabolites) may be linked to the genetic background of specific mice. We request an Agilent 6890 GC having a split/splitless all glass injector connected to a flame ionization detector as well as a 5973 mass selective detector enabling us to quantitate cholesterol/sterols/fatty acids and to analyze the metabolic profiles of congenic and genetically altered mice as a means to link genomics with metabolic phenotypes with emphasis on susceptibility to atherosclerosis. This equipment is needed to replace the Davis lab's 19 year old Hewlett-Packard 5890A GC having a split/splitless all glass injector connected to a flame ionization detector as well as a 5970 mass selective detector. During the past 3 years, the Davis lab has spent over $8000 to have this instrument repeatedly fixed using salvaged parts. Unfortunately, this was a waste of time and money, as many parts to the machine were outdated and replacement not possible. We have now have been forced to agree with Agilent that our old machine can not be fixed in a reliable manner. It is for this reason that we seek funds to purchase a replacement GC/mass spectrometer. Each lab has used GC sterol analysis as shown in table 1. Because of our dependence on this technique, prior to breaking down we used the GC -60% of the time. The projected use of each investigator is shown in table 1 and will account for 100% time use. Therefore, we have no alternative equipment for this essential technique.